1. Field of the Invention
The present invention relates to an ink jet printing apparatus that performs a suction-based recovery operation for an ink ejection print head, and a print head recovery device and a print head recovery method that are employed to perform the suction-based recovery operation.
2. Description of the Related Art
For an ink jet printing apparatus that prints an image by employing a print head wherein ink can be ejected from ejection ports formed at nozzle tips, a suction-based recovery operation is well known as a recovery operation for maintaining an appropriate ink ejection state for the print head. The suction-based recovery operation is an operation wherein, while the ejection ports of the print head are covered with a cap (a capping state), a negative pressure is generated by a pump and is introduced into the cap to move, by suction, ink that does not contribute to the printing of an image from the ejection ports into the cap. When the suction-based operation is performed, bubbles generated in the nozzles, and viscous ink and foreign substances, such as dust, in the nozzles can be discharged to maintain an appropriate ink ejection state.
According to a printing apparatus described in Japanese Patent Laid-Open No. 2007-118508, after a suction-based recovery operation has been performed, and while the capping state of a print head is being maintained, a suction pump is halted to relax the pressure in the print head and in the cap, and thereafter, an atmosphere communication valve, for connecting the interior of the cap with the atmosphere, is opened. Sequentially, then, in the state wherein the atmosphere communication valve has been opened, the suction pump is restarted to introduce external air into the cap via the atmosphere communication valve, and this air stream is employed to clean an ejection port face of the print head, where the ejection ports are formed at the nozzle tips.
However, in the printing apparatus described in Japanese Patent Laid-Open No. 2007-118508, during a period following the suction-based recovery operation and lasting until the atmosphere communication valve has been opened, the suction pump is merely halted to relax the pressure in the print head and the pressure in the cap. Therefore, when the pressure in the two components is relaxed, the pressure in the cap will be slightly lower than the atmosphere, and in this state, the pressure in the print head and the pressure in the cap are evenly balanced, so that ink will not be discharged from the ejection ports into the cap. However, when in this state the atmosphere communication valve is opened, the pressure in the cap rises, and balance is lost between the pressure in the print head and the pressure in the cap. Thus, there is a possibility that air, introduced through the atmosphere communication valve, and foreign substances in the cap, such as dust and viscous ink, will enter the print head through the ejection ports.